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Thetford C263 cassette seal


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For the second time we've found dirty water under the cassette when pulling it out to empty. I assume it's leaking on the seal between the bowl and cassette with the only seal being part of the cassette. For the moment I've put some silicone grease around the seal and bottom of the bowl but will have to replace the seal at some point. 


Has anyone changed one? The instructions from Thetford say you have to remove the whole rotating holding plate to replace the seal. So piss around and change to seal which seems a bit long winded, replace the whole holding plate as an assembly (£72) or just buy a new cassette (£115)

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9 hours ago, booke23 said:

I'd probably just replace the seal for all it costs. I've never actually done it but it can't be too hard on the C263 with the way the whole seal mechanism is removable. 


Handy video guide here:




Thanks. I came across that video and he certainly makes it look easy. Except I couldn't get the mechanism to turn. Perhaps I wasn't trying hard enough. Have ordered a seal, all of £14.99, and try again.

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I recently had to remove the whole plate and replace it with a new one which I got under warranty from Thetford. It's very difficult to turn and there was no way I could turn it just using the slide as a lever and my hands on the various small plastic tabs sticking up. Instead I had to open the flap and stick my hand into the hole to get a decent grip on it. 


The new one was slightly easier to put in. I think midland chandlers told me they were about 45 -50 quid so it might be worth checking with them.

Edited by blackrose
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